type enum in C++
A type enum is used to define a list of values or several logically constant set of values.
In the end, this set is considered as a new type of data with several possible values that can only be chosen from.
The type is enum very useful if you want to build code that is only dedicated to dealing with a specific type of values. And he ran the code, the language translator C++ Runtime will prevent it and give it an error.
In general, if you want to define a set of related values that are impossible to change, the best option is to define these values primarily within enum.
Examples of some immutable information in life that are also immutable in logic are:
seasons (Autumn, Winter, Spring, Summer)
directione (North - South - East - West)
week days (Mon-Tuesday-Wednesday etc..)
months of the year (January - February - March etc..)
sex ( Male Female )
When dealing with this fixed type of data that we do not want anyone to tamper with, we use the type enum and this is what we will see later in the examples.
method definition enum in C++
Definition enum is very similar to the method of definition struct , but dealing with the variables that we put in it later is what differs.
When you put variables inside it you can give them values yourself or let the compiler give them default values itself.
By default, the variables you set are given values in order starting from zero, for example, the first variable is its value 0 , the second is its value 1 , and so on.
In the following example, we have defined enum its name Days representing the days of the week.
Then we created an object from it and made it equal to one of the constants in Days and then print its value.
Example
#include <iostream>
using namespace std;
// we put 7 Days constants named enum here we have defined
enum Days
{
Monday,
Tuesday,
Wednesday,
Thursday,
Friday,
Saturday,
Sunday
};
int main()
{
// Just Days and its purpose is to store one of the values in today called Days. Here we created an object from
days today;
// today in the Days object which is originally on Monday here we have stored the value of the constant
today = Monday;
// today here we have printed the value of the object
cout << "today value = " << today;
return 0;
}
• We will get the following result when running.
today value = 0
In the previous example, you might say why all this torment!
Why don't we define the variable today directly as follows?!
int today = 0;
important information
In the previous example, if you declared today it as a regular variable, you could put any value in it like 20 or any other value.
The benefit of defining today an object Days is that you are forced to use the constants in it to specify a value today , which makes you guarantee that no random value can be passed other than the values that you specified. For example, in the previous example, you can change the value of the object today as follows.
// Days because it is already there in Monday you can put the value today = Monday; // Days because it is originally in Friday you can put the value today = Friday;
Important concepts about gender enum in C-Plus Plus
first concept
Here we put an example showing how to set values for the constants set in enum and how to take advantage of these values.
If you want to set values for the constants that you intend to put in enum yourself instead of the default values set by the compiler, you can put integers as values for them.
Note: You cannot put text values (words or sentences) as values for the constants we put in it.
In the following example, we have defined enum its name Months . It contains constants representing the months of the year and the number of days in it.
Then we created an object from it and made it equal to one of the constants (ie the months) in Months and then print its value.
Example
#include <iostream>
using namespace std;
// We put 12 constants in it and give them the values of Months called enum. Here we have defined
enum Months
{
Jan = 31,
Feb = 28,
Mar = 31,
Apr = 30,
May = 31,
Jun = 30,
Jul = 31,
Aug = 31,
Sep = 30,
Oct = 31,
Nov = 30,
Dec = 31
};
int main()
{
// Just Months and its purpose is to store one of the values in selectedMonth called Months. Here we created an object from
Months selectedMonth;
// selectedMonth in the Months object which is basically in May here we have stored the value of the constant
selectedMonth = May;
// May which is the number of days in the month selectedMonth Here we have printed the value of the constant
cout << "May contain " << selectedMonth << " days";
return 0;
}
• We will get the following result when running.
May contain 31 days
second concept
Here we have put an example that teaches you how to check the value of the object we create from enum using the syntax switch , which makes writing the code much easier and clearer.
One of the things that distinguishes the type enum is that the syntax can be used switch to check the value of the object we are creating from it, which makes writing the code easier and clearer.
In the following example, we have defined enum its name Days representing the days of the week.
Then we created an object from it and made it equal to one of the constants (days) in Days.
Finally, we used the sentence switch to check the value of the object and based on it we print the appropriate sentence.
Example
#include <iostream>
using namespace std;
// we put 7 Days constants named enum here we have defined
enum Days
{
Monday,
Tuesday,
Wednesday,
Thursday,
Friday,
Saturday,
Sunday
};
int main()
{
// Just Days and its purpose is to store one of the values in selectedDay called Days. Here we created an object from
Days selectedDay;
// selectedDay in the Days object which is basically on Thursday here we have stored the value of the constant
selectedDay = Thursday;
// selectedDay Here we have checked the object's value
switch(selectedDay)
{
// The next print command will be executed Thursday, Wednesday, Tuesday, or Monday if it is equal to the value of the constant
case Monday:
case Tuesday:
case Wednesday:
case Thursday:
cout << "We are available from 8:00 AM to 4:00 PM.";
break;
// The next print command will be executed Friday if it is equal to the value of the constant
case Friday:
cout << "We are available from 8:00 AM to 12:00 PM.";
break;
// And here the next print command will be executed Sunday or Saturday, if it is not equal to any previous value, then it is equal to
default:
cout << "We are not available on vacations.";
break;
}
return 0;
}
• We will get the following result when running.
We are available from 8:00 AM to 4:00 PM.
The third concept
Here we have an example showing how to define a function that takes a parameter of its type enum and how to pass a value to it when it is called.
The following example shows how to define a function that takes a parameter of its type enum and how to pass a value to it when it is called.
In the following example, we have defined enum its name Gender representing the genders (male, female).
Then we defined a function whose name printInstructions() when called, we pass an object to it, and it Gender checks its value, and on its basis it prints a specific text.
Finally, we create an object from Gender and pass it to the function printInstructions().
Example
#include <iostream>
using namespace std;
// we put in it two constants Gender named enum here we define
enum Gender
{
Male,
Female
};
// Gender When it is called we must pass it a value which is an object from the printInstructions Here we have defined a function named
void printInstructions(Gender gender)
{
// The print command set here will be executed Male equal to gender if the value we passed to it in the object
if (gender == Male)
{
cout << "Males should go to right building.";
}
// The print command set here will be executed Male not equal to gender if the value we passed to it in the object
else
{
cout << "Females should go to the left building.";
}
}
// main() Here we have defined the function
int main()
{
// just Gender and its purpose is to store one of the values in selectedGender called Gender. Here we created an object from
Gender selectedGender;
// selectedGender in the Gender object which is basically in Male here we have stored the value of the constant
selectedGender = Male;
// which will check its value and then print a sentence that fits its selectedGender value and pass the printInstructions() object here we called the function
printInstructions(selectedGender);
return 0;
}
• We will get the following result when running.
Males should go to right building.